Remove frontend build-version plumbing

The backend status endpoint already reports the shared git hash and
environment, so the SPA no longer needs its own baked copy.

frontend/src/lib/version.ts

@@ -1,5 +0,0 @@
-declare const __GIT_COMMIT_HASH__: string;
-
-export const GIT_COMMIT_HASH = __GIT_COMMIT_HASH__;
-export const APP_ENV = import.meta.env.DEV ? "dev" : "prod";
-export const APP_VERSION = `${APP_ENV} @ ${GIT_COMMIT_HASH}`;

frontend/vite.config.ts

@@ -1,30 +1,13 @@
-import { execSync } from "node:child_process";
 import { fileURLToPath, URL } from "node:url";
 
 import tailwindcss from "@tailwindcss/vite";
 import react from "@vitejs/plugin-react";
 import { defineConfig } from "vite";
 
-function gitCommitHash(): string {
-  try {
-    return execSync("git rev-parse --short HEAD", {
-      cwd: fileURLToPath(new URL(".", import.meta.url)),
-      stdio: ["ignore", "pipe", "ignore"],
-    })
-      .toString()
-      .trim();
-  } catch {
-    return "unknown";
-  }
-}
-
 const backend = process.env.VITE_BACKEND ?? "http://127.0.0.1:8000";
 
 // https://vite.dev/config/
 export default defineConfig({
-  define: {
-    __GIT_COMMIT_HASH__: JSON.stringify(gitCommitHash()),
-  },
   plugins: [react(), tailwindcss()],
   resolve: {
     alias: {